1. Field of the Invention
The present invention relates to a tape cassette and more particularly, a tape cassette suitable for use with a magnetic recording/reproducing apparatus, e.g. a video tape recorder.
2. Description of the Prior Art
In common arrangements, a tape cassette for use with a magnetic tape device such as a video tape recorder has encased therein a magnetic tape of which a forwardly exposed portion is arranged in the front of a casing along a path defined by a space between a front lid and an inner lid of the casing (for example, as disclosed in Japanese Patent Laid-open Publication 63-175279 (1988)).
The conventional tape cassette has one opening provided in the front thereof and extending approximately throughout the width thereof. The exposed portion of the magnetic tape which is protected between the front and inner lids can thus be guided through the opening with guiding members.
The front lid is mounted for pivotal movement by a pivot pin.
In addition, the front lid has a pair of brackets mounted in the upper inner side thereof. The inner lid has at both ends a couple of support pins which are engaged in the two brackets, respectively, so that the inner lid can turn about the support pins.
The inner lid also has at both ends a couple of left and right guide pins which are slidably engaged in guiding grooves provided in the casing. The left and right guiding grooves are arranged symmetrically with respect to the center line of the casing. Also, the relation between the support pins and the guiding pins has symmetry.
Each of the guiding members is fabricated by forming a resin into a semicircular shape for providing a wider area for tape passage.
The conventional tape cassette is provided with a locking member pivotably mounted on the casing for prevention of inadvertent opening of the front lid. The locking member is urged by a plate spring toward a forward leaning.
The front lid has a projection arranged on the side thereof for engagement with a hook of the locking member and can thus be prevented from rotating.
A tape cassette positioning portion is arranged at the front of the casing, where the locking member is not mounted, for determining the position of the tape cassette during loading.
The operation of such a conventional tape cassette having the foregoing arrangement will now be described.
When the tape cassette is loaded into a video tape recorder (referred to as a VTR hereinafter), the positioning portion arranged in the front of its casing comes into contact with a cassette stopper provided in the VTR and remains secured. Simultaneously, the locking member is allowed by a lock releasing member of the VTR to rotate against the urging force of the spring. As a result, the front lid is unlocked and turned upward.
As the front lid is opened, the inner lid moves upward with its support pins turning about the pivot pins. Also, its guide pins travel along their respective guiding grooves until the inner lid is completely opened and a loading post assembly of the VTR moves into the opening of the tape cassette.
The above is a description of the operation of loading the cassette into a VTR. The unloading will be carried out in reverse order of the loading.
However, the following disadvantages are inherent in the conventional tape cassette.
(1) The semicircular resin guiding members are provided for widening the tape path area to ease the feeding of the tape from the casing. This provides low guiding accuracy. Also, such an arrangement is critically affected by unfavorable environmental changes and suffers from deterioration with time and thus, damage to the tape will hardly be avoided. If the semicircular guiding post members are made of metallic materials, their production will create another difficulty and the overall cost will be increased.
If the guiding post members are of simple cylindrical shaped metal, the tape path area becomes reduced and the arrangement in the VTR will be greatly restricted in terms of freedom of design.
(2) The single opening in the casing restricts the tape loading path or the tape loading mechanism. For example, the use of an M loading arrangement, e.g. in the VHS VTR system, which is compact in size and mechanically simple, requires a wider opening of the tape cassette. If the opening in the casing is small with respect to the overall width of the tape cassette, the M loading arrangement will encounter great difficulty.
On the other hand, if the opening is widened, the forwardly exposed portion of the tape will easily be deflected causing direct contact with the inner lid. Accordingly, the opening cannot be widened arbitrarily or damage to the tape may result.
Another conventional tape cassette is disclosed in the Japanese Patent Laid-open Publication 60-214488 (1985) and has three openings arranged in its casing so as to solving the above problems. When this tape cassette is used with a U loading arrangement, e.g. of the .beta. or 8 mm VTR system, a plurality of guiding posts have to move across its three openings for loading. This loading operation can be facilitated by mounting the plural posts on one ring member. At the same time, the shape of the openings should have symmetry and extend continuously and widely for ensuring the efficient movement of the ring. However, the openings of the conventional tape cassette are narrow in width, are spaced apart from each other, and are not symmetrical. Also, they are not favorable in appearance.
(3) The locking member for prevention of inadvertent opening of the front lid and the positioning portion for determining the position of the tape cassette in loading are provided in different locations. This allows both the positional relation between the locking member and the positioning portion of the tape cassette and the positional relation between the positioning stopper and the lock releasing member of the VTR to develop an error in combination and thus, the locking and unlocking action will be conducted with less accuracy.